Electrochromic devices, which change in optical transmissivity as a result of applied voltage and current, are in use today in electrochromic windows and in automotive mirrors. Windows for buildings are often made as integrated glazing units (IGUs), which provide thermal insulation for the building and have an inner pane of glass and an outer pane of glass held apart by a spacer. A secondary seal typically surrounds the spacer. This works well for integrated glazing units of ordinary windows without electrochromic devices, with the spacer and the secondary seal hermetically sealing the two panes of glass and preventing moisture condensation in the inner space between the two panes. Electrical connections to bus bars of electrochromic devices pose design challenges, in an integrated glazing unit that should maintain hermetic sealing.
Electrochromic devices that are deposited as multiple thin layers on a single glass or plastic substrate require certain elements to make the necessary electrical connections. For example, physical vapor deposition (e.g., sputtering) can be used to deposit conductive and electrochromic layers to create an entire electrochromic device stack (e.g., bottom transparent conductor, electrochromic materials, ion conductor, top transparent conductor) on a single substrate. In some cases, vias are etched through one or more of the upper layers of the stack to expose the contacts to the lower layers of the stack that are buried beneath the upper layers in the stack so that all necessary electrical contacts are exposed. In other cases, masks are used during the deposition of the upper layers of the stack to expose the contacts to the lower layers of the stack so that all necessary electrical contacts are exposed.
Electrochromic devices that utilize electrochromic material contained within a chamber, which is defined by glass or plastic substrates with conductive layers and a peripheral edge seal, require different elements to make the necessary electrical connection. In some cases, metal clips are used to make electrical contact to the device. For example, electrochromic devices for automobile mirrors can use metal clips which function as both electrical connection and to improve the mechanical connection between the glass or plastic substrates of the device.
Electrochromic device assemblies can also be attached or laminated to additional pieces of glass or plastic to incorporate into different types of products. For example, an electrochromic device fabricated on a single sheet of glass, which is not heat strengthened or tempered, can be laminated to a second piece of tempered glass, and that laminated glass assembly can be attached to a glass lite via a spacer and secondary seal to form an IGU. Laminating a device substrate, which is not heat strengthened or tempered, to a piece of to the tempered glass increases the strength of the IGU to tolerate the required stresses experienced in operation. By way of further example, an electrochromic device with electrochromic materials disposed between two pieces of glass, which are not heat strengthened or tempered, can be laminated to a third piece of tempered glass, and that three piece of glass assembly can be attached to a glass lite using a spacer and secondary seal to form an IGU.
It is within this context that the embodiments arise.